#include<iostream>
#include<iomanip>
#include<cmath>
using namespace std;
int main()
{int N;double a[1000];double k;
 cin>>N;
 for(int i=1;i<=N;i++)
    cin>>a[i];
 if(1==N)  cout<<setiosflags(ios::fixed)<<setprecision(3)<<a[1]<<endl;
 else 
 {
  double t;
    for(int j=1;j<=N-1;j++)
       {for(int h=1;h<=N-j;h++)
          if(a[h]>a[h+1])  
          {t=a[h];a[h]=a[h+1];a[h+1]=t;}
    }
 k=2*sqrt( (double) a[N]*a[N-1]  );
 for(int m=N-2;m>=1;m--)
    k=2*sqrt((double) k*a[m]);
 cout<<setiosflags(ios::fixed)<<setprecision(3);
 cout<<k<<endl;
}
system("pause");
return 0;
}

 
